1. Field of the Invention
The present invention relates to a wafer support plate which supports a thinned semiconductor wafer, and with which the crystal orientation of the semiconductor wafer can be recognized.
2. Related Art
A semiconductor wafer is worked via many processes. A cut-away portion called a “notch” is sometimes formed in the outer periphery of the semiconductor wafer in order that the crystal orientation of this semiconductor wafer may be realizable in the course of the working as seen in JP-A-7-014912 (FIG. 4).
However, when the outer periphery of the semiconductor wafer has chipped on account of grinding, there is the problem that the notch becomes indistinguishable from the chipping and the crystal orientation becomes unrecognizable as the result. Therefore, it has also been proposed that, besides the notch, a mark for recognizing the crystal orientation be formed in the semiconductor wafer as seen in JP-A-2001-267193.
In recent years, however, semiconductor wafers have needed to be ground as thin as below 100 μm or even below 50 μm for the purpose of reducing the sizes and lightening the weights of various electronic equipment. When the semiconductor wafer is ground so thin, chipping appears in the outer periphery of the semiconductor wafer and is indistinguishable from a notch formed in this semiconductor wafer, resulting in the problem that the treatment of the ground semiconductor wafer becomes complicated. Another problem is that the rigidity of the semiconductor wafer lowers drastically, so the handling thereof becomes difficult.
Especially with a technique called “pre-dicing” wherein dicing grooves whose depth corresponds to the thickness of semiconductor chips are formed in the front surface of the semiconductor wafer beforehand, and wherein the rear surface of the semiconductor wafer is ground until the dicing grooves appear from the side of the rear surface, to thereby divide the semiconductor wafer into the individual semiconductor chips, the rigidity is lost by the division of the semiconductor wafer into the individual pieces, and the handling of this semiconductor wafer becomes very difficult. Moreover, innumerable pieces of chipping appear in the outer periphery of the divided semiconductor wafer, the crystal orientation of the semiconductor wafer becomes quite unrecognizable, and the subsequent treatment becomes more complicated.